AT&T and Verizon subscribers have noticed in recent days that Wireless Tether, a tethering app (formerly) available via the Android Market, has disappeared. Users are, however, able to find the app via the online version of Android Market, signaling that individual carriers may be to blame for the disappearance.

Google spokespeople say that while Wireless Tether is not officially blocked, Android users on specific carriers may find that the app is unavailable. Verizon and AT&T have been similarly evasive in their responses, declining to comment on whether they approached Google on getting the application removed.

Of course, carriers' efforts to crack down on illicit tethering are nothing new. AT&T recently began targeting subscribers that it suspected were using unlawful tethering programs. Via tethering apps like Wireless Tether and MyWi, users are able to evade official tethering plans like AT&T's Data Pro, which offers 4 GB of data for $45 per month.

But the news is perhaps more interesting for Google, which has traditionally taken a stance against the efforts of carriers to prohibit how customer data is allocated.